1. Field of the Invention
The present invention relates to an ultrasonic color Doppler imaging system, and more particularly, to an ultrasonic color Doppler imaging system capable of discriminating an artery and a vein, in which a blood stream velocity detected during imaging of the blood stream is used to discern the type of a blood vessel such as an artery or a vein and display the discerned result.
2. Description of the Related Art
Recently, an ultrasonic diagnostic system is widely used in a general medical treatment field. The ultrasonic diagnostic system uses phenomena such as reflection, scattering and absorption occurring when an ultrasonic wave passes through a living organism texture. The scattered signal contains acousto-impedance difference information at the boundary where a scattering occurs or movement velocity information of a scattering body. A dispersion intensity corresponding to an intensity of an actual reception signal reflects an acousto-impedance difference, and a frequency shift amount due to a Doppler effect reflects a movement velocity, more specifically, a velocity component with respect to a travelling direction of an ultrasonic beam.
A Doppler diagnostic apparatus being a kind of an ultrasonic diagnostic apparatus displays in an image form a frequency shift amount together with a signal dispersion intensity, to thereby estimate the dynamic functions in the living body. In particular, the color Doppler imaging system capable of displaying an ultrasonic color image demodulates a received signal and then digitizes the demodulated signal to process the digitized result, by which a blood stream flowing in the heart or in a main blood vessel can be described as a two-dimensional (2D) image in a real time. The color Doppler imaging system can display both tomogram and blood stream information. To identify the tomogram and the blood stream information from each other, the color Doppler imaging system displays the tomogram in monochrome and the blood stream information in colors.
When a blood stream distribution is displayed in the above color Doppler imaging system, the blood stream flowing toward the travelling direction of an ultrasonic beam emitted from a transducer is displayed as a blue color and that flowing toward the counter-direction thereof is displayed as a red color. The color Doppler imaging system displays the brightness of a color differently according to the blood stream velocity, in which the faster the brighter, and the slower the darker.
However, the above method in which the blood stream information is displayed according to the travelling direction of the ultrasonic beam can discriminate only the direction and velocity of the blood stream, but cannot discriminate whether the blood vessel of the blood stream is either a vein or an artery.